Process to upgrade partially converted vacuum residua

ABSTRACT

Processes for upgrading partially converted vacuum residua hydrocarbon feeds are disclosed. The upgrading processes may include: steam stripping the partially converted vacuum residua to generate a first distillate and a first residuum; solvent deasphalting the first residuum stream to generate a deasphalted oil and an asphaltenes fraction; vacuum fractionating the deasphalted oil to recover a deasphalted gas oil distillate and a heavy deasphalted residuum; contacting the first distillate and the deasphalted gas oil distillate and hydrogen in the presence of a first hydroconversion catalyst to produce a product; contacting the heavy deasphalted residuum stream and hydrogen in the presence of a second hydroconversion catalyst to produce an effluent; and fractionating the effluent to recover a hydrocracked atmospheric residua and a hydrocracked atmospheric distillate.

CROSS-REFERENCE TO RELATED APPLICATION

This application, pursuant to 35 U.S.C. § 120, claims benefit as adivisional to U.S. patent application Ser. No. 14/550,384 filed Nov. 21,2014, now U.S. Pat. No. 9,695,369, which is incorporated by reference inits entirety.

BACKGROUND

Hydrocarbon compounds are useful for a number of purposes. Inparticular, hydrocarbon compounds are useful, inter alia, as fuels,solvents, degreasers, cleaning agents, and polymer precursors. The mostimportant source of hydrocarbon compounds is petroleum crude oil.Refining of crude oil into separate hydrocarbon compound fractions is awell-known processing technique.

Crude oils range widely in their composition and physical and chemicalproperties. Heavy crudes are characterized by a relatively highviscosity, low API gravity, and high percentage of high boilingcomponents (i.e., having a normal boiling point of greater than 510° C.(950° F.)).

Refined petroleum products generally have higher average hydrogen tocarbon ratios on a molecular basis. Therefore, the upgrading of apetroleum refinery hydrocarbon fraction is generally classified into oneof two categories: hydrogen addition and carbon rejection. Hydrogenaddition is performed by processes such as hydrocracking andhydrotreating. Carbon rejection processes typically produce a stream ofrejected high carbon material which may be a liquid or a solid; e.g.,coke for fuel or metallurgical applications.

The higher end boiling point components, sometimes referred to asbottom-of the-barrel components, may be converted using various upstreamconversion processes. In some embodiments, vacuum residua streams may bepartially converted. The vacuum residua streams, however, may only bepartially converted in order to prevent significant downtimes inprocesses downstream due to fouling and deposition of carbonaceousdeposits.

Hydrocracking processes can be used to upgrade higher boiling materialswithin the partially converted vacuum residua by converting them intomore valuable lower boiling materials. For example, a partiallyconverted vacuum residua fed to a hydrocracking reactor may be convertedto a hydrocracking reaction product. The unreacted partially convertedvacuum resid may be recovered from the hydrocracking process and eitherremoved or recycled back to the hydrocracking reactor in order toincrease the overall vacuum residua conversion.

The conversion of partially converted vacuum residua in a hydrocrackingreactor can depend on a variety of factors, including feedstockcomposition; the type of reactor used; the reaction severity, includingtemperature and pressure conditions; reactor space velocity; andcatalyst type and performance. In particular, the reaction severity maybe used to increase the conversion. However, as the reaction severityincreases, side reactions may occur inside the hydrocracking reactor toproduce various byproducts in the form of coke precursors, sediments(i.e., precipitated asphaltenes, and other deposits) as well asbyproducts which may form a secondary liquid phase. Excessive formationof such sediments can hinder subsequent processing and can deactivatethe hydrocracking catalyst by poisoning, coking, or fouling,Deactivation of the hydrocracking catalyst can not only significantlyreduce the residua conversion, but can also require more frequentchange-outs of expensive catalysts. Formation of a secondary liquidphase not only deactivates the hydrocracking catalyst, but also limitsthe maximum conversion, thereby resulting in a higher catalystconsumption, and which can defluidize ebullated-bed catalysts. Thisleads to formation of “hot zones” within the catalyst bed, exacerbatingthe formation of coke deposits, which further deactivates thehydrocracking catalyst.

Sediment formation inside the hydrocracking reactor is also a strongfunction of the feedstock quality. For example, asphaltenes that may bepresent in the partially converted vacuum residua feed to thehydrocracking reactor system are especially prone to forming sedimentswhen subjected to severe operating conditions. Thus, separation of theasphaltenes from the partially converted vacuum residua in order toincrease the conversion may be desirable.

One type of process that may be used to remove such asphaltenes from thepartially converted vacuum residua feed is solvent deasphalting. Forexample, solvent deasphalting typically involves physically separatingthe lighter hydrocarbons and the heavier hydrocarbons includingasphaltenes based on their relative affinities for the solvent. A lightsolvent, such as a C₃ to C₇ hydrocarbon, can be used to dissolve orsuspend the lighter hydrocarbons, commonly referred to as deasphaltedoil, allowing the asphaltenes to transfer into a separate phase. The twophases are then separated and the solvent is recovered. Additionalinformation on solvent deasphalting conditions, solvents and operationsmay be obtained from U.S. Pat. Nos. 4,239,616; 4,440,633; 4,354,922;4,354,928; and 4,516,281.

Several methods for integrating solvent deasphalting with hydrocrackingin order to remove asphaltenes from vacuum residua are available. Suchprocesses are disclosed in U.S. Pat. No. 7,214,308 which disclosecontacting the vacuum residua feed in a solvent deasphalting system toseparate the asphaltenes from deasphalted oil. The deasphalted oil andthe asphaltenes are then each reacted in separate hydrocracking reactorsystems.

Moderate overall vacuum residua conversions (about 65% to 70% asdescribed in U.S. Pat. No. 7,214,308) may be achieved using suchprocesses, as both the deasphalted oil and the asphaltenes areseparately hydrocracked. However, the hydrocracking of asphaltenes asdisclosed is at high severity/high conversion, and may present specialchallenges, as discussed above. For example, operating the asphalteneshydrocracker at high severity in order to increase the conversion mayalso cause a high rate of sediment formation, and a high rate ofcatalyst replacement. In contrast, operating the asphalteneshydrocracker at low severity will suppress sediment formation, but theper-pass conversion of asphaltenes will be lower.

Processes for upgrading virgin residua hydrocarbon feeds are describedin U.S. Pat. No. 8,287,720 which describes hydroprocessing virginresidua in a first reaction unit, solvent deasphalting the effluent, andfeeding the deasphalted effluent to a second reaction unit. However, thehydrocracking of residua hydrocarbon feeds and the subsequent processsteps are operated at conditions which strain the operating units andproduce products having less desirable qualities.

In order to achieve a higher overall partially converted vacuum residuaconversion, such processes typically require a high recycle rate of theunreacted partially converted vacuum resid back to one or more of thehydrocracking reactors. Such high-volume recycle can significantlyincrease the size of the hydrocracking reactor and/or the upstreamsolvent deasphalting system.

SUMMARY OF THE DISCLOSURE

Partially converted vacuum residuum has been found to be significantlydifferent from virgin vacuum resid in terms of reactivity andprocessability. Partially converted vacuum residua may be difficult tohydrocrack while still achieving high residua conversion. Furthermore,improving the economics of partially converted vacuum residua-fedhydrocracking processes may be desired, for example, reducing theoverall equipment size of hydrocracking reactors and/or solventdeasphalters, improving the quality of the vacuum distillates asfeedstocks to distillate hydrocrackers, improving the operability of thedistillate hydrocrackers, reducing the operating severity in thedistillate hydrocrackers, and requiring less frequent hydrocrackingcatalyst change-outs.

Processes according to embodiments herein have been found effective inprocessing partially converted vacuum residua and the like, in someembodiments, to greater than 87.5%, 92.5%, 95% or even 97% overallvacuum residua conversion.

In one aspect, embodiments disclosed herein relate to a process forupgrading a partially converted vacuum residua. The process may includethe following steps: stripping the partially converted vacuum residua togenerate a first distillate and a first residuum; solvent deasphaltingthe first residuum to generate a deasphalted oil and an asphaltenesfraction; vacuum fractionating the deasphalted oil to recover adeasphalted gas oil distillate and a heavy deasphalted residuum;contacting the first distillate and the deasphalted gas oil distillateand hydrogen in the presence of a first hydroprocessing catalyst toproduce a first hydroprocessing effluent; contacting the heavydeasphalted residuum and hydrogen in the presence of a secondhydroconversion catalyst to produce a second hydroprocessing effluent;and fractionating the second hydroprocessing effluent to recover ahydrocracked atmospheric residua and a hydrocracked atmosphericdistillate.

In another aspect, embodiments disclosed herein relate to a process forupgrading a partially converted vacuum residua. The process may includethe following steps: stripping with a mass transfer device the partiallyconverted vacuum residua to generate a first distillate and a firstresiduum; deasphalting with a solvent deasphalting unit the firstresiduum to generate a deasphalted oil and an asphaltenes fraction;fractionating with a vacuum fractionation unit the deasphalted oil torecover a deasphalted gas oil distillate and a heavy deasphaltedresiduum; contacting the first distillate and the deasphalted gas oildistillate and hydrogen in the presence of a first hydroprocessingcatalyst an ebullated bed hydroconversion reactor to produce a firsthydroprocessing effluent; contacting the heavy deasphalted residuum andhydrogen in the presence of a second hydroconversion catalyst in a fixedbed hydroconversion reactor system to produce a second hydroprocessingeffluent; and fractionating with an atmospheric fractionation unit thesecond hydroprocessing effluent to recover a hydrocracked atmosphericresidua and a hydrocracked atmospheric distillate.

In another aspect, embodiments disclosed herein relate to a system forupgrading partially converted residuum hydrocarbons. The system mayinclude the following components: a mass transfer device to strip apartially converted residuum hydrocarbon stream into a first distillatestream and a first residuum stream; a solvent deasphalting unit forrecovering a deasphalted oil stream and an asphaltenes stream from thefirst residuum stream; a vacuum fractionation unit to fractionate thedeasphalted oil stream to recover a deasphalted gas oil stream and aheavy deasphalted residuum stream; an ebullated bed hydroconversionreactor system for contacting the heavy deasphalted residuum stream andhydrogen with a first hydroconversion catalyst to produce a firsteffluent; an atmospheric fractionation unit to fractionate the firsteffluent to recover a hydrocarbon atmospheric distillate stream and ahydrocarbon atmospheric residuum stream; a fixed bed hydroconversionreactor system for contacting at least one of the first distillatestream, the deasphalted gas oil stream, and the hydrocarbon atmosphericdistillate stream to produce a second effluent.

Other aspects and advantages will be apparent from the followingdescription and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified flow diagram of current hydrocracking anddeasphalting processes for upgrading virgin vacuum residua according toembodiments disclosed herein.

FIG. 2 is a simplified flow diagram of a hydrocracking and deasphaltingprocess for upgrading partially converted vacuum residua according toembodiments disclosed herein.

FIG. 3 is a simplified flow diagram of a hydrocracking and deasphaltingprocess for upgrading partially converted vacuum residua according toembodiments disclosed herein.

DETAILED DESCRIPTION

Embodiments disclosed herein relate generally to processes for upgradingpartially converted heavy petroleum feedstocks. In one aspect,embodiments disclosed herein relate to processes for hydrocracking anddeasphalting partially converted vacuum residua. In other aspects,embodiments disclosed herein relate to processes for increasing theconversion of residua feedstocks to about 95% or about 98%.

Partially converted vacuum residuum hydrocarbon (resid) feedstocksuseful in embodiments disclosed herein may include various heavy crudeand refinery fractions which have been previously processed in one ormore conversion processes to at least partially convert some of thehydrocarbons therein. For example, partially converted vacuum residuahydrocarbon feedstocks may include vacuum residua hydrocarbon feedswhich have been partially processed in hydrocracking units, vac residuacoking units, hydrothermolysis units, hydropyrolysis units, pyrolysisunits, oil shale retorting units, biomass pyrolysis units, biomasshydropyrolysis units, biomass hydrothermolysis units, tar sandsextraction units, steam assisted gravity drainage processes, toe to heelair injection processes, an in situ petroleum extraction processes, or acombination thereof, each of which may be process derived, hydrocracked,partially desulfurized, and/or low-metal streams. The above partiallyconverted vacuum residua feedstocks may include various impurities,including asphaltenes, metals, organic sulfur, organic nitrogen, andConradson carbon residue (CCR). The initial boiling point of thepartially converted vacuum residua is typically greater than about 510°C. (900° F.), about 537° C. (1000° F.) or about 565° C. (1050° F.).

Partially converted vacuum residua feedstocks are chemically differentfrom virgin vacuum residua feedstocks. The partially converted vacuumresidua feedstocks may be provided from virgin vacuum residua feedstocksprocessed in one or more upstream conversion processes. Easy-to-convertspecies are typically already converted in the upstream conversionprocesses, resulting in the partially converted vacuum residuafeedstocks containing quantities of difficult-to-convert species. Thesedifficult-to-convert species typically require high reaction severity toconvert to higher value hydrocarbons. The high reaction severity mayincrease side reactions typically making it difficult to achieve thehigh overall conversions, provided by the solutions discussed below. Theside reactions form byproducts which harm the catalyst and/or producesediment. By use of partially converted vacuum residua feedstocks andsteam stripping of such feedstocks while incorporating a downstreamsolvent deasphalting unit and a downstream ebullated-bed unit tohydrocrack the deasphalted vacuum residua, the recovered hydroprocessedvacuum gas oils will have better properties and will ease conditions inthe downstream fixed-bed distillate hydroprocessing unit. In someembodiments, the polynuclear cyclic index (PCI) which quantitates thepolynuclear aromatics concentration in heavy petroleum oils, maydecrease in the vacuum gas oil produced from the process and theproduction of diesel may be increased. Downstream processing units mayoperate at lower pressures and those that utilize catalyst may improvetheir catalyst cycle length.

Processes according to embodiments disclosed herein for conversion ofpartially converted vacuum residua hydrocarbon feedstocks to lighterhydrocarbons include initially steam stripping the feedstock into afirst distillate stream and a first residuum stream. The first residuumstream may then be separated in a solvent deasphalting unit to recover adeasphalted oil fraction and an asphaltenes fraction. The solventdeasphalting unit may be, for example, as described in one or more ofU.S. Pat. Nos. 4,239,616, 4,440,633, 4,354,922, 4,354,928, 4,536,283,and 7,214,308, each of which is incorporated herein by reference to theextent not contradictory to embodiments disclosed herein. In the solventdeasphalting unit, a light hydrocarbon solvent may be used toselectively dissolve desired components of the first residuum and rejectthe asphaltenes. In some embodiments, the light hydrocarbon solvent maybe a C₃ to C₇ hydrocarbon, and may include propane, butane, isobutane,pentane, isopentane, hexane, heptane, and mixtures thereof. In someembodiments, the solvent may be an aromatic solvent or a mixture of gasoils or a light naphtha produced in the process itself or available inthe refinery.

The deasphalted oil fraction may be fractionated to recover adeasphalted gas oil distillate stream and a heavy deasphalted residuumstream. The deasphalted gas oil distillate stream may be reacted withhydrogen over a hydrocracking catalyst in a distillate hydroprocessingreaction unit to convert at least a portion of the hydrocarbons tolighter molecules, such as, but not limited to a naphtha fraction, akerosene fraction, and a diesel fraction. The heavy deasphalted residuumstream may be reacted with hydrogen over a hydrocracking catalyst in adeasphalted vacuum residua hydrocracking reaction unit to convert atleast a portion of the hydrocarbons to lighter molecules.

Catalysts used in the distillate hydroprocessing reaction unit and thedeasphalted vacuum residua hydrocracking reaction unit may be the sameor different. Suitable hydrotreating and hydrocracking catalysts usefulin the distillate hydroprocessing reaction unit and the deasphaltedvacuum residua hydrocracking reaction unit may include one or moreelements selected from Groups 4-12 of the Periodic Table of theElements. In some embodiments, the hydrotreating and hydrocrackingcatalysts according to embodiments disclosed herein may comprise,consist of, or consist essentially of one or more of nickel, cobalt,tungsten, molybdenum and combinations thereof, either unsupported orsupported on a porous substrate such as silica, alumina, titania, orcombinations thereof. As supplied from a manufacturer or as resultingfrom a regeneration process, the hydroconversion catalysts may be in theform of metal oxides, for example. If necessary or desired, the metaloxides may be converted to metal sulfides prior to or during use. Insome embodiments, the hydrocracking catalysts may be pre-sulfided and/orpre-conditioned prior to introduction to the hydrocracking reactor. Forexample, one or more catalysts as described in U.S. Pat. Nos. 4,990,243,5,069,890, 5,071,805, 5,073,530, 5,141,909, 5,277,793, 5,366,615,5,439,860, 5,593,570, 6,860,986, 6,902,664, and 6,872,685 may be used inembodiments herein, each of which are incorporated herein by referencewith respect to the hydrocracking catalysts described therein.

The distillate hydroprocessing reaction unit may include one or morereactors in series and/or parallel. Reactors suitable for use in thedistillate hydroprocessing reaction unit may include any type ofhydroprocessing reactor. Asphaltenes may be present in the deasphaltedgas oil distillate stream only to a minor extent, thus a wide variety ofreactor types may be used in the first reaction unit. For instance, afixed bed reactor may be considered where the metals and Conradsoncarbon residue of the deasphalted gas oil distillate stream fed to thefirst hydrocracking reaction unit is less than 100 wppm and 10%,respectively. The number of reactors required may depend on the feedrate, and the level of conversion desired in the distillatehydroprocessing reaction unit. In some embodiments, the distillatehydroprocessing reaction unit is a single fixed bed reactor. In someembodiments, the catalysts used in the distillate hydroprocessingreaction unit may include distillate hydrotreating catalysts in extrudedforms which may contain zeolitic components as well as conventionalNi/Co/Mo/W on oxide supports. In other embodiments, catalysts which maybe used in the distillate hydroprocessing reaction unit are as describedin one or more of U.S. Pat. Nos. 4,990,243, 5,069,890, 5,071,805,5,073,530, 5,141,909, 5,277,793, 5,366,615, 5,439,860, 5,593,570,6,860,986, 6,902,664, and 6,872,685, each of which are incorporatedherein by reference with respect to the hydrocracking catalystsdescribed therein. The distillate hydroprocessing reaction unit upgradesvacuum gas oils, atmospheric gas oils and diesel components produced inother units of the system.

The deasphalted vacuum residua hydrocracking reaction unit may includeone or more reactors in series and/for parallel. Reactors suitable foruse in the deasphalted vacuum residua hydrocracking reaction unit mayinclude any type of hydrocracking reactor, including ebullated bedreactors, fluidized bed reactors, slurry reactors and moving bedreactors, among others. The number of reactors required may depend onthe feed rate, the overall target vacuum residua conversion level, andthe level of conversion desired. In some embodiments, the deasphaltedvacuum residua hydrocracking reaction unit may be one or more ebullatedbed reactor. In some embodiments, the catalyst in the deasphalted vacuumresidua hydrocracking reaction unit may be an amorphous catalyst whichis fluidizable, having a pore size distribution amenable to high metalscontent and high CCR content feedstocks. In other embodiments, thecatalyst in the deasphalted vacuum residua hydrocracking reaction unitmay be a dispersed phase or slurry catalyst including molybdenum sulfidetype materials. In yet other embodiments, the catalyst in thedeasphalted vacuum residua hydrocracking reaction unit may include oneor more elements selected from Groups 4-12 of the Periodic Table of theElements. In some embodiments, the catalyst in the deasphalted vacuumresidua hydrocracking reaction unit may comprise, consist of, or consistessentially of one or more of nickel, cobalt, tungsten, molybdenum andcombinations thereof, either unsupported or supported on a poroussubstrate such as silica, alumina, titania, or combinations thereof.

The reaction product from the deasphalted vacuum residua hydrocrackingreaction unit may then be separated to recover a hydrocrackedatmospheric distillate stream and a hydrocracked atmospheric residuastream, the latter of which includes unreacted partially convertedvacuum residua feed, asphaltenes, and any resid-boiling range productsresulting from hydrocracking of the asphaltenes contained in thepartially converted vacuum residua feedstock. Distillate hydrocarbonfractions recovered may include, among others, atmospheric distillates,such as hydrocarbons having a normal boiling temperature of less thanabout 343° C., and vacuum distillates, such as hydrocarbons having anormal boiling temperature of less than from about 482° C. to about 566°C. In some embodiments, the hydrocracked atmospheric distillate streammay be fed to the first hydrotreating/hydrocracking reaction unit.

Processes according to embodiments disclosed herein thus include asolvent deasphalting unit upstream of the first and second hydrocrackingreaction units, providing for conversion of at least a portion of theasphaltenes to lighter, more valuable hydrocarbons. Hydrocracking ofdeasphalted gas oil distillate streams and heavy deasphalted residuumstream may provide for overall vacuum residua conversions that may, begreater than about 60 wt % in some embodiments; greater than 80 wt % inother embodiments; greater than 90 wt % in other embodiments; greaterthan 92.5 wt % in other embodiments; greater than 95 wt % in yet otherembodiments; and greater than 98 wt % in yet other embodiments. Theoverall vacuum residua conversion is defined as the % conversion ordisappearance of 510° C.+(or 538° C.+ or 566° C.+) components from avirgin vacuum residua feed to the upstream bottom-of-the-barrelconversion unit, i.e., stream 100, relative to the net amount in asolvent deasphalter bottoms stream 20, the latter quantity of whichrepresents the 40% or 20% or 10% or 7.5% or 5% or 2% of the materialthat remains unconverted in embodiments disclosed herein.

The distillate hydroprocessing reaction unit may be operated at atemperature in the range from about 360° C. to about 440° C.; from about380°V to about 430° C. in other embodiments. Hydrogen partial pressuremay be in the range from about 100 ban to about 200 bara in someembodiments; from about 125 to about 155 bara in other embodiments. Thehydroprocessing reactions may also be conducted at a liquid hourly spacevelocity (LHSV) in the range from about 0.1 hr⁻¹ to about 3.0 hr⁻¹ insome embodiments; from about 0.2 hr⁻¹ to about 2 hr⁻¹ in otherembodiments. The hydroprocessing reactions may also be conducted at ahydrogen to oil ratio of about 5,000 to about 20,000 scf/bbl. In someembodiments, the distillate hydroprocessing reaction unit may processone or more distillate streams, or combinations thereof. The distillatehydroprocessing reaction unit may include a combination of hydrotreatingand hydrocracking catalysts. If the end point of the feed is less thanabout 343° C., hydrotreating catalyst may be used. If the feed includesvacuum distillates, such as those boiling above 343° C., a combinationof hydrotreating and vacuum gas oil hydrocracking catalysts may be used.

In some embodiments, if the distillate hydroprocessing reaction unit isan ebullated bed unit, the reactors may operate at temperatures in therange from about 380° C. to about 450° C., hydrogen partial pressures inthe range from about 70 barn to about 170 bare, and liquid hourly spacevelocities (LHSV) in the range from about 0.2 hr⁻¹ to about 2.0 h⁻¹

The deasphalted vacuum residua hydrocracking reaction unit may beoperated at a temperature in the range from about 360° C. to about 480°C.; from about 400° C. to about 450° C. in other embodiments. Pressuresin each of the first and second reaction units may be in the range fromabout 70 bars to about 230 bara in some embodiments; from about 100 toabout 180 bare in other embodiments. The hydrocracking reactions mayalso be conducted at a liquid hourly space velocity (LHSV) in the rangefrom about 0.1 hr⁻¹ to about 3.0 hr⁻¹ in some embodiments; from about0.2 hr⁻¹ to about 2 hr⁻¹ in other embodiments. The hydrocrackingreactions may also be conducted at a hydrogen to oil ratio of about5,000 to about 20,000 scf/bbl.

In some embodiments, operating conditions in the distillatehydroprocessing unit may be less severe than those used in thedeasphalted vacuum residua hydrocracking unit, thus avoiding excessivecatalyst replacement rates. Accordingly, overall catalyst replacement(i.e., for both units combined) is also reduced. For example, thetemperature in the distillate hydroprocessing unit may be less than thetemperature in the deasphalted vacuum residua hydrocracking unit.Operating conditions may be selected based upon the partially convertedvacuum residua feedstock, including the content of impurities in thepartially converted vacuum residua feedstock and the desired level ofimpurities to be removed in the distillate hydroprocessing unit, amongother factors. In some embodiments, vacuum residua conversion in thedeasphalted vacuum residua hydrocracking unit may be in the range fromabout 50 to about 75 wt %; from about 55 to about 70 wt % in otherembodiments; and from about 60 to about 65 wt % in yet otherembodiments, in addition to hydrocracking the partially converted resid,sulfur and metal removal may each be in the range from about 40% toabout 75%, and Conradson carbon removal may be in the range from about30% to about 60%, In other embodiments, at least one of an operatingtemperature and an operating pressure in the deasphalted vacuum residuahydrocracking unit may be greater than used in the distillatehydroprocessing unit.

Using process flow schemes according to embodiments disclosed herein,overall vacuum residua conversions of at least 80%, 90%, 92.5% 95%, 98%or higher may be attained, which is a significant improvement over whatcan be achieved with a two-unit hydrocracking system alone.

Referring now to FIG. 1, a simplified process flow diagram of currentprocesses for upgrading virgin vacuum resid according to embodimentsdisclosed herein is illustrated. A virgin resid and hydrogen may be fedvia flow lines 310 and 312, respectively, to a first hydrocrackingreaction stage 314 containing a hydrocracking catalyst and operating ata temperature and pressure sufficient to convert at least a portion ofthe resid to lighter hydrocarbons. The first stage reactor effluent maybe recovered via flow line 316. The first stage effluent may includereaction products and unreacted resid, which may include unreacted feedcomponents such as asphaltenes, and hydrocracked asphaltenes havingvarious boiling points, including those in the boiling range of theresid feedstock.

The first hydrocracking reaction stage 314 may include one or morereactors in series and/or parallel. Reactors suitable for use in thefirst hydrotreating and hydrocracking reaction stage may includeebullated bed reactors. In some embodiments, the first hydrocrackingreaction stage 314 includes only a single ebullated bed reactor.

A deasphalted oil fraction and hydrogen may be fed via flow lines 318and 380, respectively, to a second hydrocracking reaction stage 322containing a hydrocracking catalyst and operating at a temperature andpressure to convert at least a portion of the deasphalted oil to lighterhydrocarbons. The second stage reactor effluent may be recovered viaflow line 324.

The second hydrocracking reaction stage 322 may include one or morereactors in series and/or parallel. Reactors suitable for use in thesecond hydrocracking reaction stage may include ebullated bed reactors.The number of reactors required may depend on the feed rate, the overalltarget resid conversion level, and the level of conversion attained inthe first hydrocracking reaction stage. In some embodiments, the secondhydrocracking reaction stage 322 includes only a single ebullated bedreactor.

The first stage reactor effluent and the second stage reactor effluentmay be fed via flow lines 316, 324 to separation system 326. Theatmospheric distillates may be recovered via flow line 356. The vacuumdistillates may be recovered via flow line 362, and the second bottomsfraction may be recovered via flow line 330 and processed in the solventdeasphalting unit 332 as described above for solvent deasphalting unit32. The deasphalted oil fraction 318 may be sent to the secondhydrocracking reaction stage 322 and the pitch 320 may be recovered.

Referring now to FIG. 2, a simplified process flow diagram of processesfor upgrading partially converted vacuum residua according toembodiments disclosed herein is illustrated. Pumps, valves, heatexchangers, and other equipment are not shown for ease of illustrationof embodiments disclosed herein.

In some embodiments, a vacuum residua hydrocarbon feedstock may be fedto an upstream process which produces an effluent including thepartially converted vacuum residua hydrocarbon feedstock. The upstreamprocess converts some of the heavier components in the vacuum residuahydrocarbon feedstock.

In some embodiments, an effluent from an upstream process 70 mayinitially be fed to a high pressure high temperature separator 80 (HP/HTseparator) via flow line 100. The effluent 100 may be a partiallyconverted vacuum residua. The partially converted vacuum residuafeedstock may be derived from any of a variety of upstream feedprocessing units which partially convert residua feeds. These processesare sometimes called “bottom of the barrel processes.” These bottom ofthe barrel processes may include an upstream hydrocracking unit, vacresid coking unit, a hydrothermolysis unit, a hydropyrolysis unit, apyrolysis unit, an oil shale retorting process, a biomass pyrolysisprocess, a biomass hydropyrolysis process, a biomass hydrothermolysisprocess, a tar sands extraction process, or combinations thereof. Thepartially converted vacuum residua may also be derived from heavy oilstreams produced by steam assisted gravity drainage, toe to heel airinjection, an in situ petroleum extraction process, or any combinationthereof. In some embodiments, the upstream hydrocracking unit may be anebullated bed hydrocracking unit, a fixed bed hydrocracking unit, or amoving bed hydrocracking unit.

The HP/HT separator 80 may be located upstream of a mass transfer device12. The HP/HT separator 80 separates the partially converted vacuumresidua from the upstream process into a vapor fraction and a liquidfraction. The flashed liquid fraction of the partially converted vacuumresidua, is fed via flow line 10 to the mass transfer device 12 togenerate a first distillate and a first residuum. The vapor fraction maybe recovered via flow line 82 and fed to the distillate hydroprocessingreaction unit 14.

The mass transfer device 12 may be a column, such as, but not limitedto, a packed tower, an unpacked tower, or a tray column. In someembodiments, the mass transfer device 12 may be a stripping tower. Astripping medium may be fed to the stripping tower 12 via flow line 33.The stripping medium may be, but is not limited to, a non-reactivestripping medium, such as steam, hydrogen, nitrogen or fuel gas. If thestripping medium is steam, the steam may be superheated high pressuresteam. The temperature of the steam may range from about 232° C. (450°F.) to about 371° C. (700° F.). The steam may be fed to the masstransfer device 12 through line 33 at a rate ranging from about 3 toabout 20 pounds of steam/barrel of feed (about 13 to about 9.1 kg ofsteam/barrel of feed). The first distillate stream may have an ASTMD-1160 final boiling point in the range from about 427° C. (800° F.) toabout 482° C. (900° F.). The first residuum stream may have acorresponding ASTM D-1160 initial boiling point in the range from about800° F. to about 900° F.

From the stripping tower 12, the first distillate may be fed via flowline 15 to a distillate hydroprocessing reaction unit 14 containing ahydrotreating catalyst, a hydrocracking catalyst, or combinationsthereof. Hydrogen may be added to the distillate hydroprocessingreaction unit 14 via flow line 13. The distillate hydroprocessingreaction unit 14 may operate at a temperature and pressure sufficient toconvert at least a portion of the first distillate to lighterhydrocarbons. The distillate hydroprocessing reaction unit effluent, ora first hydroprocessing effluent, may be recovered via flow line 17. Asdescribed above, the distillate hydroprocessing reaction unit effluentmay include hydroprocessed distillate products, which may include, butnot limited to, hydrocarbons boiling in the range of a naphtha fraction,a kerosene fraction, and a diesel fraction. In some embodiments, thedistillate hydroprocessing reaction unit effluent may be fractionated toprovide the fractions listed. In some embodiments, the distillatehydroprocessing reaction unit 14 is a single fixed bed reactor.

From the stripping tower 12, the first residuum may be fed via flow line16 to a solvent deasphalting (SDA) unit 32 to produce a deasphalted oilfraction and an asphaltenes fraction. The deasphalted oil fraction maybe recovered from solvent deasphalting unit 32 via flow fine 18 and fedto a vacuum fractionation tower 60. The vacuum fractionation tower 60provides a deasphalted gas oil and a heavy deasphalted residuum. Thedeasphalted gas oil stream may have an ASTM D-1160 final boiling pointin the range from about 510° C. (950° F.) to about 566° C. (1050° F.).The heavy deasphalted residuum stream may have an ASTM D-1160 initialboiling point ranging from about 510° C. (950° F.) to about 566° C.(1050° F.).

In some embodiments, the asphaltenes fraction may be recovered from theSDA unit 32 via flow fine 20 and further processed. In otherembodiments, the asphaltenes fraction may be recovered via flow line 20and fed to a gasification unit (not shown) to produce a synthesis gas.The synthesis gas may be fed directly to or converted to hydrogen foruse in one or more of the distillate hydroprocessing reaction unit 14 orthe deasphalted vacuum residua hydrocracking unit 22. In someembodiments, the gasification unit may be such as those described inU.S. Pat. Nos. 8,083,519 and 7,993,131.

The deasphalted gas oil may be fed via flow line 26 to the distillatehydroprocessing reaction unit 14. The deasphalted vacuum residuum may befed via flow line 30 to a deasphalted vacuum residua hydrocrackingreaction unit 22. Hydrogen may be added to the deasphalted vacuumresidua hydrocracking reaction unit 22 via flow line 19. The deasphaltedvacuum residua hydrocracking reaction unit 22 may be an ebullated bedreaction system having one or more ebullated bed reactors or a slurryreactor system having one or more slurry reactors. The deasphaltedvacuum residua reactor effluent, or second hydroprocessing effluent, maybe recovered via flow line 24 and fed to separation system 28. Theseparation system 28 may separate the vapor and liquid. The vapor may berecovered via flow line 56 and the liquid may be recovered via flow line58. Optionally, the vapor may be directed to the firsthydrotreating/hydrocracking reaction unit 14 and the liquid may bedirected to the SDA 32.

In some embodiments, separation system 28 may include a high pressurehigh temperature separator 40 (HP/HT separator) for separating thesecond unit reactor effluent liquid and vapor. The separated vapor maybe recovered via flow line 42, and the separated liquid may be recoveredvia flow line 44.

The separated liquid stream may then be fed via flow line 44 to anatmospheric distillation tower 54 to separate the stream into a fractionincluding hydrocarbons boiling in a range of atmospheric distillates andan atmospheric residuum fraction including hydrocarbons having a normalboiling point of at least 343° C. The atmospheric distillates may berecovered via flow line 56, and the atmospheric residuum fraction may berecovered via flow line 58. Optionally, the separated vapor via flowline 42 and the vapor via flow line 56 may be directed to the distillatehydroprocessing reaction unit 14 via flow line 57.

The atmospheric distillates may be fed to the distillate hydroprocessingreaction unit 14 and processed along with the deasphalted gas oil andthe first distillate. In some embodiments, the atmospheric distillates,the deasphalted gas oil and the first distillate may be fedindependently to the distillate hydroprocessing reaction unit 14 or maybe combined upstream of the distillate hydroprocessing reaction unit 14prior to entering the distillate hydroprocessing reaction unit 14. Insome embodiments, the atmospheric residuum fraction may be combined withthe first residuum and fed to the SDA unit 32. In some embodiments, theatmospheric residuum fraction and the first residuum may be fedindependently to SDA unit 32 or may be combined upstream of the SDA unitprior to entering the SDA unit 32.

The vapor fraction from the HP/HT separator 80, the first distillatefrom the stripping tower 12, and the deasphalted gas oil from the vacuumfractionation tower 60 may be combined and fed to the distillatehydroprocessing reaction unit 14 or those streams may be fedindependently to the distillate hydroprocessing reaction unit 14.Optionally, the atmospheric distillates from the separation system 28may be combined with the vapor fraction from the HP/HT separator 80, thefirst distillate from the stripping tower 12, and the deasphalted gasoil from the vacuum fractionation tower 60 and fed to the distillatehydroprocessing reaction unit 14 or those streams may be fedindependently to the distillate hydroprocessing reaction unit 14.

Referring now to FIG. 3, a simplified process flow diagram of processesfor upgrading partially converted vacuum residua according toembodiments disclosed herein is illustrated, where like numeralsrepresent like parts. The partially converted vacuum residua fromupstream bottom-of-the-barrel processes may be produced from a tarsands-derived bitumen stream. The tar sands-derived bitumen stream isfed via flow line 200 along with a diluent stream having an end boilingpoint lower than 510° C. and preferably lower than 343° C. via flow line210 to the upstream bottom-of-the-barrel process 70. In someembodiments, the effluent from the upstream bottom-of-the-barrel process70 may generate a synthetic crude oil containing distillate boilingmaterial and at least a partially converted vacuum residua component.The synthetic crude oil may be fed through flow line 100 to the HP/FITseparator 80 to recover the diluent stream via flow line 210; thedistillate stream via flow line 82 and the flashed liquid fraction ofthe partially converted vacuum residua via flow line 10. The diluent maybe recycled back to the upstream bottom-of-the-barrel process 70.

EXAMPLES

In an exemplary embodiment, the process according to FIG. 1 may haveabout 40,000 BPSD of virgin vacuum residua fed via line 310 to firsthydrocracking reaction stage 314. The first hydrocracking reaction stage314 may operate at a temperature and pressure sufficient to convertabout 52% of the vacuum residua. The SDA 332 may be operated in such amanner and with such solvents to achieve a DAO lift between about 70 toabout 80%. The second hydrocracking reaction stage 322 may operate attemperature and pressure sufficient to convert from about 75 to about85% of the DAO. The prospective overall flowrates and properties for themajor, intermediate and product streams are summarized in Table 1 below:

TABLE 1 Stream 330 318 320 356 362 BPSD 18858 15505 3353 21264 18120 APIGravity 4.93 9.07 −9.85 40.3 18.03 Specific Gravity 1.037 1.007 1.1630.8236 0.9463 Sulfur, wt % 1.45 1.18 2.5 0.094 0.515 Nitrogen, wt % 0.650.435 1.5 0.081 0.34 CCR, wt % 23.0 14.2 58.4 — 0.56 Ni + V, wppm 148 31615 — <2

The Polynuclear Cyclic Index (PCI) quantifies the polynuclear aromaticsconcentrations in heavy petroleum oils. The PCI of a straight run VGOmay have a value of about 2000 to about 4000. The processed vacuum gasoil fraction in line 362 may have a PCI value of about greater thanabout 9,000 and as high as about 15,000 to about 16,000, depending uponthe distillation end point of the VGO and the source of the crude oilused to generate the straight run VGO. The increased PCI index of theprocessed vacuum gas oil fraction in line 362 may increase thedifficulty for upgrading to diesel and other middle distillates usingconventional fixed-bed hydrotreaters/hydrocrackers. Fixed-bedhydrotreaters/hydrocrackers designs for high PCI feeds may require atleast one of the following: frequent catalyst changeouts, i.e., veryshort on-stream times of the order of 12 months or less; extremely highhydrogen partial pressures, such as about 25 to about 40% higher thanfor straight run VGO fixed-bed hydrotreaters/hydrocrackers; orprohibitively expensive catalyst loadings of from about 100 to about200% higher than for straight run VGO fixed-bedhydrotreaters/hydrocrackers. If the processed vacuum gas oil fraction inline 362 is fed to a fixed-bed hydrotreater/hydrocracker for maximumdiesel production rather than processing in a fluid catalytic cracking(FCC) unit, an increase from about 20 to about 25% in the diesel yieldmay be expected. In other words, feeding 40,000 BPSD of virgin vacuumresid to the process in FIG. 1 and including a fixedhydrotreater/hydrocracker to process the processed vacuum gas oilfraction may result in an increase of 28,000 BPSD of diesel.

In comparison, the process according to FIG. 2 may have about 40,000BPSD of virgin vacuum residua fed to upstream bottom-of-the-barrelprocess 70. The mass transfer device 12 may be a steam stripper operatedat a stem/oil ratio of about 0.03 kg/kg and a pressure of about 2 bar.The SDA 32 may be operated to achieve an about 86% lvol % lift. Theasphaltenes fraction from the SDA unit 32, via flow line 20, may begasified to produce synthesis gas, may be combusted in a fluid bedboiler to generate steam, or may be fed to a delayed coker. Thedeasphalted vacuum residua hydrocracking unit 22 may be operated toachieve about 85% conversion. The prospective overall flowrates andproperties for the major, intermediate and product streams aresummarized in Table 2 below:

TABLE 2 Stream Combined 16 58 16 + 58 26 20 BPSD 24000 6000 30000 260073993 API Gravity 8.3 14.75 9.56 12.63 −7.29 Specific Gravity 1.012 0.9671.002 0.9817 1.139 Sulfur, wt % 1.29 0.28 1.075 0.87 2.26 Nitrogen, wt %0.61 0.39 0.562 0.42 1.38 CCR, wt % 17.3 12.7 115.2 8.2 54.5 Ni + V,wppm 119 10 98 18.2 541

The vacuum gas oil produced from feeding partially converted vacuumresidua according to the process of FIG. 2 has a much lower PCI form thevacuum gas oil produced according to the process of FIG. 1 as shown inTable 3 below:

TABLE 3 Stream 362 (FIG. 1) 15, 26 and 56 (FIG. 2) API Gravity 18.0318.5 Specific Gravity 0.9463 0.9433 Sulfur, wt % 0.515 0.49 Nitrogen, wt% 0.34 0.32 CCR, wt % 0.56 0.4 Ni + V, wppm 9000 3000

As shown above the vacuum gas oil produced from feeding partiallyconverted vacuum residua according to the process of FIG. 2 may beprocessed in distillate hydroprocessing reaction unit 14 at conventionalhydrogen partial pressure, space velocities and catalyst on streamtimes. The process according to embodiments of FIG. 1, compared toembodiments of FIG. 3, may provide one or more of the following:increasing diesel production rates from about 28,000 to about 33,400BPSD, a 193% relative increase; improving the catalyst cycle length ofthe fixed-bed hydrotreaters/hydrocrackers 14 by about 12 to about 24months; reducing the hydrogen partial pressures of the fixed-bedhydrotreaters/hydrocrackers 14 by about 25%; and reducing the PCI of thevacuum gas oil by about 663%.

As described above, embodiments disclosed herein provide for theefficient conversion of heavy hydrocarbons to lighter hydrocarbons viaan integrated hydrocracking and solvent deasphalting process. Morespecifically, embodiments described herein provide an efficient andeffective means for upgrading hard-to-convert species in feedstocksderived from other partial conversion processes. Advantageously, thepartially converted vacuum residua feedstock may be processed separatelyfrom a virgin-like vacuum residua feed, thereby addressing the issuesthat may arise with the feeds having different compositions. Processflexibility may be provided by handling the virgin vacuum residua andthe partially converted vacuum residuum in different trains. Theflexibility may be found by tailoring the operating conditions for thespecific feed. The sizing of the process units may also be reduced byhaving the feeds in different trains. The hard to process species may behandled without large volumes of recycle.

In one aspect, processes according to embodiments disclosed herein maybe useful for attaining a high overall feed conversion in ahydrocracking process, such as greater than 87%, 92%, 95% or 97% overallvacuum residua conversion.

While the disclosure includes a limited number of embodiments, thoseskilled in the art, having benefit of this disclosure, will appreciatethat other embodiments may be devised which do not depart from the scopeof the present disclosure. Accordingly, the scope should be limited onlyby the attached claims.

What is claimed:
 1. A system for upgrading partially converted residuumhydrocarbons, the system comprising: a mass transfer device to strip apartially converted residuum hydrocarbon stream into a first distillatestream and a first residuum stream; a solvent deasphalting unit forrecovering a deasphalted oil stream and an asphaltenes stream from thefirst residuum stream; a vacuum fractionation unit to fractionate thedeasphalted oil stream to recover a deasphalted gas oil stream and aheavy deasphalted residuum stream; an ebullated bed hydroconversionreactor system for contacting the heavy deasphalted residuum stream andhydrogen with a first hydroconversion catalyst to produce a firsteffluent; an atmospheric fractionation unit to fractionate the firsteffluent to recover a hydrocarbon atmospheric distillate stream and ahydrocarbon atmospheric residuum stream; a fixed bed hydroconversionreactor system for contacting at least one of the first distillatestream, the deasphalted gas oil stream, and the hydrocarbon atmosphericdistillate stream to produce a second effluent.
 2. The system of claim1, further comprising a gasification system for converting theasphaltenes stream to a synthesis gas.
 3. The system of claim 1, furthercomprising an upstream conversion unit to convert a residuum stream tothe partially converted residuum hydrocarbon stream.
 4. The system ofclaim 3, wherein the upstream conversion unit is selected from the groupconsisting of a hydrocracking unit, a vac resid coking unit, ahydrothermolysis unit, a hydropyrolysis unit, a pyrolysis unit, an oilshale retorting unit, a biomass pyrolysis unit, a biomass hydropyrolysisunit, a biomass hydrothermolysis unit, a tar sands extraction unit, asteam assisted gravity drainage process, a toe to heel air injectionprocess, an in situ petroleum extraction processes, or a combinationthereof.
 5. The system of claim 1, wherein the mass transfer devicecomprises a stripping tower.
 6. The system of claim 4, wherein thehydrocracking unit comprises an ebullated bed, a fixed-bed or amoving-bed hydrocracking unit.
 7. The system of claim 1, furthercomprising a high temperature/high pressure separator upstream of thesteam stripper to produce the partially converted residuum hydrocarbonstream.
 8. The system of claim 7, wherein a vapor fraction from the hightemperature/high pressure separator is fed to the fixed bedhydroconversion reactor system.
 9. The system of claim 1, furthercomprising a high temperature/high pressure separator upstream of theatmospheric fractionation unit to recover a vapor fraction and a liquidfraction from the first effluent of the ebullated bed hydroconversionreactor system.
 10. The system of claim 9, wherein the vapor fractionfrom the high temperature/high pressure separator is fed to the fixedbed hydroconversion reactor system.
 11. The system of claim 9, whereinthe liquid fraction from the high temperature/high pressure separator isfed to the atmospheric fractionation unit.